A bipedal cooperative drive method for the stick-slip piezoelectric actuator to achieve smooth motion.

Existing kinds of stepping piezoelectric actuators have difficulty in maintaining smooth stepping characteristics in motion, especially with applied loads, because they are limited by their driving principle and structural design. However, non-smooth stepping characteristics not only reduce the output performance of piezoelectric actuators but also greatly limit the applications of piezoelectric actuators. In this paper, a bipedal cooperative drive method for the stick-slip actuator is proposed to improve stepping characteristics and achieve smooth motion under different conditions. Two flexible driving feet alternately push the rotor to rotate clockwise. Experimental results show that the stepping characteristics vary with the driving voltage, and the displacement curve transitions from non-smooth to smooth to sudden jump as the driving voltage rises. Furthermore, the displacement curves can maintain good smoothness within a horizontal load range of 20-30 g. The maximum angular speed of the designed actuator is 1452 mrad/s when the driving voltage and driving frequency are 100 V and 1400 Hz, respectively. These features help broaden the practical application of actuators.

Evaluation of Three-Dimensional Surface Roughness in Microgroove Based on Bidimensional Empirical Mode Decomposition.

Micromilling is an extremely important advanced manufacturing technology in the micromanufacturing industry. Compared with the traditional milling process, micromilling has stricter requirements on the surface roughness of the workpiece, and the roughness of the microcurved surface is not easy to measure. In order to more accurately characterize the curved surface morphology of the microgrooves obtained by micromilling, this paper proposes a method to extract the reference plane of the curved surface based on the bidimensional empirical mode decomposition algorithm and characterize the three-dimensional surface roughness of the curved surface. First, we synthesize the morphologies of the microgrooves by simulated non-Gaussian rough surfaces and models of textures. Second, the bidimensional empirical mode decomposition algorithm was used to extract the reference planes of the simulated microgrooves. Third, the three-dimensional roughness parameters suitable for the curved surfaces of microgrooves were selected to establish an evaluation system. The results show that the mean squared errors of the reference planes are below 1%, so bidimensional empirical mode decomposition can effectively extract reference planes, and the evaluation system of three-dimensional surface roughness proposed in this paper reflects morphological characteristics of the curved surfaces of microgrooves more thoroughly than that of two-dimensional surface roughness parameters.

Laser-Induced Slippery Liquid-Infused Surfaces with Anticorrosion and Wear Resistance Properties on Aluminum Alloy Substrates.

Slippery liquid-infused surfaces (SLISs) are developed as a potential alternative to superhydrophobic surfaces (SHSs) to resolve the issues of poor durability in corrosion protection and wear resistance. In this work, we used a simple laser processing technology to prepare a SLIS on the aluminum alloy (7075) surface. The superhydrophobicities of the modified surface and the oil film formed by liquid injection make the corrosive medium difficult to directly contact the surface and thus have a significant effect on corrosion resistance. The water and oil repellent SLIS exhibits durable corrosion resistance and excellent tribological properties compared with the SHS. The anticorrosion and wear resistance performances provided by the composite film have been assessed by multiple methods including the electrochemical test, immersion test, and friction wear test. The results indicate that compared to the bare surface, laser-ablated surface (LAS), and fluoroalkyl silane-modified SHS, the SLIS composite coating has better corrosion resistance and wear resistance, which is of great significance to expand the potential applications of 7075 aluminum alloys. The work provides a research basis for expanding the practical application of SLISs in complex environments.

Preparation of Micro-Pit-Textured PCD Tools and Micro-Turning Experiment on SiCp/Al Composites.

Serious tool wear occurs very often during machining due to the reinforcing phases in the workpiece. In this study, micro-pit-textures were prepared on the surfaces of PCD tools with a nanosecond laser to improve their cutting performance on SiCp/Al composites. The micro-pits were designed with rounded corners to improve the chip flow. The location and size of the texture were determined by analyzing the tool-chip contact area of the non-textured tool. The cutting performance of these textured PCD tools was investigated through orthogonal cutting experiments. It was found that the optimal cutting performance of the textured tools was achieved with the proper distance of the texture from the main cutting edge (35 µm) and the pit spacing (60 µm), aa a result of which the main cutting force reduced by about 14%, and the tool wear and surface adhesion significantly reduced. This texture was then applied in the micro-turning experiments of the PCD tool on the SiCp/Al composites. The cutting force in this experiment reduced by 22%, and the textured tool provided better chip transfer and tool anti-tipping. In this study, the role of SiC particles as a third body between the tool and the chip surface is discussed.

Fabrication of durable underoil superhydrophobic surfaces with self-cleaning and oil-water separation properties.

In this study, a simple method without any additional chemical modification is proposed to fabricate underoil superhydrophobic surfaces with micro- and nano-hierarchical structures using a nanosecond laser system. The fabricated surfaces exhibited extreme superhydrophobicity and underoil superhydrophobicity with high contact angles of 153.8 ± 1.5° and 161.3 ± 1.1°, respectively. The results show that even after 20 abrasion cycles, the fabricated surfaces retained water repellency and self-cleaning performance under oil, while the superhydrophobicity in air was not resistant to wear. In addition, the fabricated brass meshes can also be used to separate oil in an oil-water mixture based on the prewetting induced underoil superhydrophobicity after being damaged. The separation efficiency was as high as 97.8%, which made them more appropriate for the oil-water separation than those based on superhydrophobicity. The proposed fabrication method is suitable for large-scale and mass production and provides a new avenue and possibility for further development of robust functional interface materials.

Study on In-Situ Tool Wear Detection during Micro End Milling Based on Machine Vision.

Most in situ tool wear monitoring methods during micro end milling rely on signals captured from the machining process to evaluate tool wear behavior; accurate positioning in the tool wear region and direct measurement of the level of wear are difficult to achieve. In this paper, an in situ monitoring system based on machine vision is designed and established to monitor tool wear behavior in micro end milling of titanium alloy Ti6Al4V. Meanwhile, types of tool wear zones during micro end milling are discussed and analyzed to obtain indicators for evaluating wear behavior. Aiming to measure such indicators, this study proposes image processing algorithms. Furthermore, the accuracy and reliability of these algorithms are verified by processing the template image of tool wear gathered during the experiment. Finally, a micro end milling experiment is performed with the verified micro end milling tool and the main wear type of the tool is understood via in-situ tool wear detection. Analyzing the measurement results of evaluation indicators of wear behavior shows the relationship between the level of wear and varying cutting time; it also gives the main influencing reasons that cause the change in each wear evaluation indicator.

Reversible Wettability between Underwater Superoleophobicity and Superhydrophobicity of Stainless Steel Mesh for Efficient Oil-Water Separation.

Design and fabrication of smart materials with reversible wettability for oil-water separation have attracted worldwide attention due to the increasingly serious water pollution problem. In this study, a rough oxide coating with micro/nanoscale structures is developed on the 304 stainless steel mesh (SSM) by laser ablation. The smart surface with ethanol immersion and natural drying treatments shows the wetting conversion between underwater superoleophobicity and superhydrophobicity. Based on the wettability transition behavior, both light and heavy oil-water mixtures can be separated with the high separation efficiency. Moreover, after being exposed to various corrosive solutions and high temperatures, the smart surface still shows prominent environmental stability. Switchable surface with excellent properties should be an optimal choice to solve the environmental conditions that need to be addressed urgently.

Bio-Inspired Design of Bi/Tridirectionally Anisotropic Sliding Superhydrophobic Titanium Alloy Surfaces.

Many biological surfaces with the multi-scale microstructure show obvious anisotropic wetting characteristics, which have many potential applications in microfluidic systems, biomedicine, and biological excitation systems. However, it is still a challenge to accurately prepare a metal microstructured surface with multidirectional anisotropy using a simple but effective method. In this paper, inspired by the microstructures of rice leaves and butterfly wings, wire electrical discharge machining was used to build dual-level (submillimeter/micrometer) periodic groove structures on the surface of titanium alloy, and then a nanometer structure was obtained after alkali-hydrothermal reaction, forming a three-level (submillimeter/micrometer/nanometer) structure. The surface shows the obvious difference of bidirectional superhydrophobic and tridirectional anisotropic sliding after modification, and the special wettability is easily adjusted by changing the spacing and angle of the inclined groove. In addition, the results indicate that the ability of water droplets to spread along parallel and perpendicular directions on the submillimeter groove structure and the different resistances generated by the inclined groove surface are the main reasons for the multi-anisotropic wettability. The research gives insights into the potential applications of metal materials with multidirectional anisotropic wetting properties.

Modeling and Experimental Study of the Localized Electrochemical Micro Additive Manufacturing Technology Based on the FluidFM.

In this work, the localized electrochemical micro additive manufacturing technology based on the FluidFM (fluidic force microscope) has been introduced to fabricate micro three-dimensional overhang metal structures at sub-micron resolution. It breaks through the localized deposition previously achieved by micro-anode precision movement, and the micro-injection of the electrolyte is achieved in a stable electric field distribution. The structure of electrochemical facilities has been designed and optimized. More importantly, the local electrochemical deposition process has been analyzed with positive source diffusion, and the mathematical modeling has been revealed in the particle conversion process. A mathematical model is proposed for the species flux under the action of pulsed pressure in an innovatively localized liquid feeding process. Besides, the linear structure, bulk structure, complex structure, and large-area structure of the additive manufacturing are analyzed separately. The experimental diameter of the deposited cylinder structure is linearly fitted. The aspect ratio of the structure is greater than 20, the surface roughness value is between 0.1-0.2 µm at the surface of bulk structures, and the abilities are verified for deposition of overhang, hollow complex structures. Moreover, this work verifies the feasibility of 3D overhang array submicron structure additive manufacturing, with the application of pulsed pressure. Furthermore, this technology opens new avenues for the direct fabrication of nano circuit interconnection, tiny sensors, and micro antennas.

Slippery liquid infused porous surfaces with corrosion resistance potential on aluminum alloy.

The slippery liquid infused porous surface has developed into a potential technology to solve the problem of poor durability in corrosion resistance. Herein, a kind of slippery liquid infused porous surface is created on 7075 aluminum alloy by wire electrical discharge machining for corrosion resistant applications. The hardness of the constructed porous microstructure is similar to the aluminum alloy substrate material, which ensures the stability of the slippery liquid infused porous surface. The modification of low surface energy substance fluorosilane avoids the direct contact between corrosive liquid and porous surface, and improves the lyophobic performance of the porous microstructure surface. The corrosion resistance of the porous microstructure surface is enhanced by the injection of perfluorinated lubricating oil. The experimental results show that the created slippery liquid infused porous surface can display super-slippery properties and durable corrosion resistance. The average sliding velocity of a water droplet is 0.48 ± 0.05 mm s-1 at a sliding angle of 5°. The corrosion current density of the surface is 3.116 × 10-6 A cm-2, which is 2 orders of magnitude lower than that of the polished surface. And the impedance radius reaches 90 kΩ cm2, which is about 20 times that of the polished surface.

Microstructure control of the wettability and adhesion of Al alloy surfaces.

This article provides a simple and fast method to adjust the wettability and adhesion of aluminum (Al) alloy surfaces after electric discharge machining (EDM). For an Al alloy plate after EDM, without any grinding and polishing, laser treatment was directly performed on the surface to prepare the Al alloy surface with different wettability and adhesion behaviors. Scanning electron microscopy was used to analyze the surface morphologies of the smooth surface, wire-cut surface, and the surface treated with different laser parameters after wire-cut. Then, the chemical composition, contact angle (CA) stability, adhesion and surface bounce behavior of the surfaces processed via different treatment steps were tested and analyzed. The results indicated that the crater structure was distributed randomly on the EDM-processed surface, with a static CA of 129 ± 1.2°. After laser engraving, the surface generates a regular arrangement of micron-level grooves/pits. Meanwhile, the molten Al alloy spattered at high temperatures and instantly solidified to produce sub-micron-sized metal particles attached to the pit/bottom of the trench and the unprocessed area, naturally forming a dual-scale structure. This naturally formed dual-scale structure makes the surface static CA up to 154.6 ± 1.2°. This technology realized that only laser treatment is used to control the wettability and adhesion of the Al alloy surface after EDM treatment and expected to provide a simple and low-cost method for the practical application of large-area superhydrophobic surfaces.

Bioinspired Reversible Switch between Underwater Superoleophobicity/Superaerophobicity and Oleophilicity/Aerophilicity and Improved Antireflective Property on the Nanosecond Laser-Ablated Superhydrophobic Titanium Surfaces.

In this work, the bioinspired reversible switch between underwater superoleophobicity/superaerophobicity and oleophilicity/aerophilicity and improved antireflective property were successfully demonstrated on the nanosecond laser-structured titanium surfaces. Titanium materials were first transformed to be superhydrophobic after nanosecond laser ablation and low-temperature annealing treatments, showing oleophilicity/aerophilicity in water. If the surfaces were prewetted with absolute ethanol and then immersed into water, the surfaces showed superoleophobicity/superaerophobicity. More importantly, the underwater oleophilicity/aerophilicity of the surfaces could be easily recovered by natural drying, and the switch between the underwater superoleophobicity/superaerophobicity and oleophilicity/aerophilicity could be repeated many cycles. Moreover, based on the original antireflective performance of the surface of the laser-ablated micro/nanoscale structures, we demonstrated that the inspired improved antireflective property could be skillfully realized by the prewetting treatment. The developed bioinspired multifunctional materials provide a versatile platform for the potential applications, such as controlling oil droplets, bubbles, and optical behavior.

Bouncing Dynamics of Impact Droplets on the Biomimetic Plane and Convex Superhydrophobic Surfaces with Dual-Level and Three-Level Structures.

Reducing the contact time of a water droplet on non-wetting surfaces has great potential in the areas of self-cleaning and anti-icing, and gradually develops into a hot issue in the field of wettability surfaces. However, the existing literature on dynamic behavior of water drops impacting on superhydrophobic surfaces with various structural shapes is insufficient. Inspired by the microstructure of lotus leaf and rice leaf, dual-level and three-level structures on plane and convex surfaces were successfully fabricated by wire electrical discharge machining on aluminum alloy. After spraying hydrophobic nanoparticles on the surfaces, the plane and convex surfaces with dual-level and three-level structures showed good superhydrophobic property. Bouncing dynamics of impact droplets on the superhydrophobic surfaces wereinvestigated, and the results indicated that the contact time of plane superhydrophobic surface with a three-level structure was minimal, which is 60.4% less than the plane superhydrophobic surface with dual-level structure. The effect of the interval S, width D, and height H of the structure on the plane superhydrophobic surface with three-level structure on contact time was evaluated to obtain the best structural parameters for reducing contact time. This research is believed to guide the direction of the structural design of the droplet impinging on solid surfaces.

Design and performance evaluation of collision protection-based safety operation for a haptic robot-assisted catheter operating system.

The robot-assisted catheter system can increase operating distance thus preventing the exposure radiation of the surgeon to X-ray for endovascular catheterization. However, few designs have considered the collision protection between the catheter tip and the vessel wall. This paper presents a novel catheter operating system based on tissue protection to prevent vessel puncture caused by collision. The integrated haptic interface not only allows the operator to feel the real force feedback, but also combines with the newly proposed collision protection mechanism (CPM) to mitigate the collision trauma. The CPM can release the catheter quickly when the measured force exceeds a certain threshold, so as to avoid the vessel puncture. A significant advantage is that the proposed mechanism can adjust the protection threshold in real time by the current according to the actual characteristics of the blood vessel. To verify the effectiveness of the tissue protection by the system, the evaluation experiments in vitro were carried out. The results show that the further collision damage can be effectively prevented by the CPM, which implies the realization of relative safe catheterization. This research provides some insights into the functional improvements of safe and reliable robot-assisted catheter systems.

Nanosecond Laser-Induced Underwater Superoleophobic and Underoil Superhydrophobic Mesh for Oil/Water Separation.

Materials with special wettability have drawn considerable attention especially in the practical application for the separation and recovery of the oily wastewater, whereas there still remain challenges of the high-cost materials, significant time, and complicated production equipment. Here, a simple method to fabricate the underwater superoleophobic and underoil superhydrophobic brass mesh via the nanosecond laser ablation is reported for the first time, which provided the micro-/nanoscale hierarchical structures. This mesh is superhydrophilic and superoleophilic in air but superoleophobic under water and superhydrophobic under oil. On the basis of the special wettability of the as-fabricated mesh, we demonstrate a proof of the light or heavy oil/water separation, and the excellent separation efficiencies (>96%) and the superior water/oil breakthrough pressure coupled with the high water/oil flux are achieved. Moreover, the nanosecond laser technique is simple and economical, and it is advisable for the large-area and mass fabrication of the underwater superoleophobic and underoil superhydrophobic mesh in the large-scale oil/water separation.

Minimally invasive approach for coronary artery fistula correction.

Objectives: Minimally invasive cardiac surgery has recently become widespread. The aim of this study is to analyse the feasibility of a minimally invasive approach for coronary artery fistula (CAF) correction. Methods: From February 2001 to June 2014, 49 patients in our centre underwent minimally invasive CAF correction without cardiopulmonary bypass (CPB). The mean age was 21.18 ± 11.24 years (range, 5 months to 64 years). Patients with cardiac anomalies who underwent CAF correction and those who underwent CAF via the minimally invasive approach with CPB were excluded. Results: There were no in-hospital mortalities or conversions to median sternotomy. Subxiphoid incisions (22 cases) and parasternal incisions (20 cases) were the most commonly used approaches for the procedure. The operative time was 67.45 ± 22.69 min (30-125 min). The intubation time was 3.72 ± 1.82 h (2-12 h), and the ICU stay was 9.67 ± 5.43 h (4-24 h). A trivial residual shunt was identified in only 1 patient during the procedure; however, this shunt had disappeared by discharge. Conclusions: The minimally invasive approach can provide excellent surgical exposure for CAF ligation in select patients. This approach is a safe and cosmetic alternative to conventional treatment and may minimize the length of stay.

Spironolactone Regulates HCN Protein Expression Through Micro-RNA-1 in Rats With Myocardial Infarction.

Emerging evidence has shown that aldosterone blockers reduced the incidence of ventricular arrhythmias in patients with myocardial infarction (MI). However, the mechanism remains unknown. In this study, we investigated the mechanism by which spironolactone, a classic aldosterone blocker, regulates hyperpolarization-activated cyclic nucleotide-gated channel (HCN) protein expression in ischemic rat myocardium after MI. Eighteen rats surviving 24 hours after MI were randomly assigned into 3 groups: MI, spironolactone, and spironolactone + antagomir-1. Six sham-operated rats had a suture loosely tied around the left coronary artery, without ligation. The border zone of the myocardial infarct was collected from each rat at 1 week after MI. HCN2 and HCN4 protein and messenger RNA (mRNA) level were measured in addition to miRNA-1 levels. Spironolactone significantly increased miRNA-1 levels and downregulated HCN2 and HCN4 protein and mRNA levels. miRNA-1 suppression with antagomir-1 increased HCN2 and HCN4 protein levels; however, HCN2 and HCN4 mRNA levels were not affected. These results suggested that spironolactone could increase miRNA-1 expression in ischemic rat myocardium after MI and that the upregulation of miRNA-1 expression partially contributed to the posttranscriptional repression of HCN protein expression, which may contribute to the effect of spironolactone to reduce the incidence of MI-associated ventricular arrhythmias.

Single cusp replacement in patients with ventricular septal defect and aortic insufficiency.

OBJECTIVE: The aim of this study was to analyze the mid- and long-term outcome of single cusp replacement in patients with ventricular septal defect and aortic insufficiency. METHODS: From September 2005 through March 2014, 172 patients underwent single cusp replacement and ventricular septal defect (VSD) closure. The median age was 19.5 years (range, 9 months to 67 years). Additional techniques were used to repair associated anomalies including sinus of Valsalva aneurysm, patent ductus arteriosus, patent foramen ovale, subaortic membrane, and intramural coronary artery. RESULTS: One patient with large left ventricle (preoperative end-diastolic diameter: 9.8 cm) died after the procedure from incurable heart failure. Four patients required a second pump run for residual aortic insufficiency (AI) (two patients, 1.16%) and residual VSD (two patients, 1.16%). Four patients required re-exploration for postoperative bleeding or cardiac tamponade. Mean follow-up was 53.27 ± 25.37 months (median, 56.5 months; range, 3 to 104 months). Redo aortic valve surgery was performed in three patients. Three patients had moderate-severe AI during the following period without reoperation. There was no post-operative endocarditis. CONCLUSION: Single cusp replacement can be safely used in patients with VSD-AI.

Chemical oxygen demand removal efficiency and limited factors study of aminosilicone polymers in a water emulsion by iron-carbon micro-electrolysis.

Micro-electrolysis was applied in the present study to investigate the effect of pH, iron-carbon mass ratio, contact time, and treatment batch on the removal efficiency of chemical oxygen demand (COD) within an aminosilicone emulsion. The results exhibited that the removal efficiency of COD decreased linearly with the batch increase, and this tendency was consistent under the various conditions. The adsorption of activated carbons contributes a large portion to the elimination of COD within the aminosilicone emulsion. The oxidation action of iron-carbon micro-electrolysis was proven and the aminosilicone emulsion's COD removal contribution was approximately 16%. Aminosilicone polymers were adsorbed on the surface of activated carbons and iron chips, which contributes to the decline of COD removal efficiency and limits the contribution of oxidation action.

[Methods for the assessment of organic compounds biodegradability: A review].

There are plenty of methods used for the assessment of organic compounds biodegradability, but lack of comprehensive literatures in systematically introducing the assessment methods and guiding the choice of the methods. This paper briefly introduced the indicative parameters in assessing organic compounds biodegradability and the assessment methods of aerobic and anaerobic biodegradation, with the focus on the principles and criteria in the choice of the assessment methods, and analyzed in detail the reasons for the differences in the biodegradation rates of organic compounds when different test methods were adopted. Taking the standards established by the Organization for Economic Co-operation and Development (OECD) as an example, the process of choosing and applying the assessment methods was introduced, the systematic method-choosing route was integrated, and the advantages of the OECD standard methods were pointed out.